Apparatus for high-frequency induction heating



NOV; 2, 1948. STORM 2,452,801

APPARATUS FOR HIGH-FREQUENCY INDUCTION HEATING Filed June 7, 44 s Shets-Sheec 1 IN V EN TOR.

Herbefijlfiifrm BY %Ctpq y Nov. 2, 1948. H. F. STORM 2,452,801

7 APPARATUS FOR HIGH-FREQUENCY INDUCTION HEATING Filed June 7, 1944 5 Sheets-Sheet 2 INVENTOR.

Herberifi i530 r272 Nov 2, 1948. H. F, STO M' 2,452,801

APPARATUS FOR HIGH-FREQUENCY INDUCTION HEATING Filed June 7, 1944 3 Sheets-Sheet 3 21 FR E ZJ ENCV Q SOURCE w Z0 COOLING FLUID IN V EN TOR.

Patented Nov. 2, 1948 MN I TED S ESS .APPARATUS. FOR HIGH-FREQUENCY INDUCTION HEATING Herbert stormg' 'rwest A'llis,'.;Wis., assignor to Sunbeam Corporation, a corporation of Illinois Application J1me 7, 1944',Serial'N0.,539,108

( Cl:i-219i-13 Z 1 Claim. 1

"Thisinvention relates to an =apparatus for high-frequency induction heatingand more particularly to an apparatus of such type for'h'e'ating'work pieces havingsharply'convex surface portions, such as edges, ribs, corners-or lugs', and concentrating the heating 'eifect at such :convex surfaces.

It often occurs that some salient portion of the surface of a mechanism is subjectin operation to intense localizedwear. It is desirable to be able to heat and temper the surface ofthe heating system is particularly-suitable iorthis purpose inasmuch as the heating effect ofsa high-frequency induction field variesfrom point to point. with the:intensityof the field. Byia proper designof the heatinginductor itsfield-- can be given the. desired intensity distribution characteristic.

While the invention is of general application, it is illustrated as applied to the local'zheating and tempering of the shoulder of a gun-bre.ech,'-'

which shoulder engages the rimof the shell .casing. By local heating and tempering of the .gun

' breech shoulders, it has been .iound that .the

number of firings of a gun embodying the. breech,

without repair or replacement,.may. be increasedmany times.

It is an object of the invention to provide new and improved high-frequency.induction heating apparatus for treating a work piece having. a

sharply convex surface portion and concentrating the heating effect at such convex surface portion.

' In accordance with the invention, a high-frequency induction heating apparatus for heating portion and for concentrating the heating over a predetermined portion of. the ccnvexsurface of the work piece comprises a support, aheatinginductor mounted on the support and pro- 'portioned to develop a high-frequency magnetic field including, in the absence of a. work piece,

a portion of maximum intensity'which is of the same order of magnitude over its cross-sectional area. The apparatus also includes positioning means mounted on the support for locating'the* work piece within the field with Ethe "predeter- ----mined convex surface portion thereof effectively cutting across the maximum intensity portion of "the field.

'Ihe invention, both as to its organization and method-0f operation; togetherwith further-obects' and advantages thereof; will best beunderstood by reference to the specification'takenin connection with the accompanying draWi-ngs in which Fig; l is aperspectiveviewof-a gun'breech "to the heat treatment=of=which the application oithe invention is illustrated;

-'Fig.--2 is a graph of-the magnetic field ofa single turn heating inductor to-a'idin the eX- 1 I planation of the invention;

Figs; 3 and 4' are graphs of the magnetic-fields of an alternativeform'of heating inductor to aid inexplaining theinvention;

F-igs5-and 6 are anend View and a front eleveLtiomrespectively, of a high-frequencydr'idizction heating apparatus embodying the invention;

Figs. 7- and 8- are detailed views-0f an alternative form *of heating inductor suitable 'for' use 'in the apparatus 'of- Figs. 5 and 6; and

*Figs." 9'- and' '10 are schematic representations -=of-' alternative forms-oiheating inductorsenew tivevto concentrate the heatingeifect'*more sharplyata single point or regionon the-surface of the workpiece.

' Referring=-now to-Fig; l of thedrawingsthere =is illustrated as a'work piece for heat treatment 'by the high-frequencyinduction heating apparatus'of theinvention a gun breech-l0 which-is essentially 'an'elongated bifurcated element having a pairof arms liia, 1 Gb joined by end bridging members tile and Hid. Each of the armsllla, 1 "l Ub has' an elongatedsharp edge 1 lie" which terface portions or" the arms.

minates in a shculderdilf; the edges tile and shoulders to! --comprising sharply 'ccnvexsur- The cross sections of thearms' item-and ifib'throughout the portions a work piece having a sharply convex surface thereof Whichare intersected by the sharp edge portions iee are elongated and the sharply convex-surfa-ce-portions my include one end of the crosssections of the arms :i-Ela, iilb at such points.

"Inthe breech-described the-regions lily of the arms lilayiilb, includingthe surface portions "treme-Wear ,in; use. Therefore it is' desired to lDL-indicatedin dotted-lines, are subject toexheat treat/these localized portions of the gun breech toiharden them and reduce Wear without substantially heat treating the remaining portions ofthe gun breech; which might tend to if the heating inductor II were disposed in the slot of the element I With the center of inductor approximately at the shoulder Ill). The field of inductor II in the absence of the work piece Illb is shown in the full lines, this being con-.'

ventional representation of a field of a single turn' coil, the field being substantially toroidal and having a portion of maximum and approximately uniform intensity within the coil. It is understood that the intensity of the field at any point is inversely proportional to the distance between adjacent field lines. presence of the work piece Illb, it is seen that Giving effect now to the the latter crowds the field primarily in the region of the surface [02' and, since the heating efiect varies directly with the intensity of the high-frequency field over the extent of the work piece, it is clear that the maximum heating effect on the work piece Illb is in the region around point Illz'. On the other hand, the intensity of the magnetic field, and therefore the heating effect, at the point if is relatively low. Therefore such an arrangement is not suitable for concentrating the heat treatment in the regions Illg of the work piece 10.

Now referring to Figs. 3 and 4, the single-turn inductor H is replaced by a pair of spaced inductors I2 and I3 excited in such a waythat their fields are in aiding phase. As indicated in Fig. 3, under such circumstances the field be-. tween the inductors I2 and I3 is an elongated approximately uniform field of -maximum intensity which approximates that of a continuous solenoid having a length equal to the spacing of the inductors I2 and I3, such a solenoid enclosing a field of substantiall uniform and maximum intensity. If now the work piece IOb is inserted between the coils as indicated in Fig. 4, effectively cutting across the maximum intensity portion of the field between the inductors l2 and I3, the high-frequency field cannot substantially penetrate the work piece Ifib, due to the skinefiect, but is pushed up or crowded around it, intensely concentrating the field at the point mi and developing a field of somewhat lesser but high intensity at the point I07. With such an arrangement, then, the heating effect of the inductors I2 and I3 is very highly concentrated at the sharply convex surface portion If and concentrated to a lesser degree at the sharply convex surface portion I07, while all other surface portions of the arm Iflb are heated to a correspondingly lesser degree.

Referring now to Figs. and 6, there is illus-- trated schematically a high-frequency heattreating apparatus embodying the principal of concentration of the heat treatment represented in Fig. 4, by means of which the heating may be concentrated over a predetermined portion of one or more sharply convex surface portions of a work piece, in the example illustrated the concentration being at a single sharply-convex surface portion of each arm of the gun breech Ill.

, Ihe apparatus of Figs. 5 and 6 comprises abase or support i l having back vertical support or flange Ida and a heating inductor I5 mounted on the support by means of rigid projecting leads or conductors I5e extending through the support I la. The inductor I 5 is proportioned to develop an elongated high-frequency magnetic field including, in the absence of a work piece, a portion of maximum intensity which is of the same order of magnitude over its cross-sectional area. To this end the inductor I5 includes two pairs of coaxial coils 1511, i512 and 150, I5d the coils of each pair being spaced and being wound and connected so that their magnetic fields are in aiding phase, while the pairs of coils are preferably wound and connected so that their fields are in opposing phase. By this arrangcment an elongated field of approximately uniform intensity is developed between the coils of each pair and extending over the area of the coils.

The apparatus of Figs. 5 and 6 also includes a positioning means for the work piece Ill which,

for the sake of clarity, is represented in dotted lines. This positioning means may be a stud l6 mounted on the support I l and having a beveled end portion Illa to facilitate sliding the work piece It over the stud IS. The positioning means I6 is effective to locate the work piece II] with each of its arms extended between the coils of one of the pair of coils and with the sharply convex surface portions or shoulders Inf thereof effectively cutting across the maximum intensity portions of the fields of the pairs of coils I511, I51) and IE0, Ifid. Specifically the location of the work piece ill with respect to the heating inductors I 5 is as represented in the cross-sectional view of Fig. 4, that is with the end of the cross section of the arms Illa, lilb included in the sharply convex surface portions or shoulders I0) approximately at the centers of the maximum intensity portions of the fields between the coils of each of the pairs I5a, I5b and I50, I5d. Further, as shown in Fig. 4 and in Fig. 5, the other end of the cross sections of the arms Ida, Illb extend outside of the inductor coils and into a portion of the field of substantially lesser intensity. V g

The coils of the heating inductor I5 and its leads I5e are preferably formed from hollow copper tubing and are connected through insulation joints H to a cooling fluid circulating pump I8.

The leads I56 are also connected to a source of high-frequency oscillations I9, connected to be energized from a power supply circuit 20 through a switch or circuit breaker 2|. Preferably, the high-frequency source I9 is of the improved form disclosed and claimed in copending application Serial No. 539,106, Herbert F. Storm, filed June the longitudinal axis of the inductor I5 and permits pivotal adjustment of the nozzles for quenching a predetermined surface portion of the work piece II] after heating. The nozzles 22 are connected through quenching fluid pipes 26 and a 5- valve Z'lfito a source of supplyof quenchingfiuid, such as pipe 28.

In operation, the heating inductor I5 is excited from the high-frequency source 19 upon connecting it through the switch 2! to the power supply circuit 20. Simultaneously, the cooling fluid pump is put into operation to circulate cooling fiuid through the hollow conductor of the inductor i5 therebyto prevent excessive heating thereof by its own high-irequency magnetic field.

Thus it will be seen the the apparatus of Figs. 5 and 6 described above comprises a high-frequency induction heatng system for heating an elongated work piece l each of the arms of which has an elongated cross section and two sharply convex surface portions I87 including one end of the cross section, that is two sharp edge portions Hie which intersect one end of the cross section Hlh. In the operation of this system the heating is substantially concentrated over a predetermined portion of the two convex surface portions or edges in the regions Ifig. This concentration of the heating is effected by developing an elongated high-frequency magnetic field between the coils of each of the pairs of coils i511, I52) and lEc, id of the heating inductor which, in the absence of the work piece, constitutes the portion of the total field of the inductor coils of maximum intensity, which intensity is of the same order of magnitude over its crosssectional area, that is over the area of the coils. The work piece is then positioned by means of the stud I6 so that the arms 59a, lilb thereof are within and extended across the fields of the pairs of inductor coils a, 55b and i5c, 15d, respectively, with the sharply convex surface portions or edges Hi thereof efiectiveiy cutting across this maximum intensity portion of the field and crowding the field, as represented in Fig. 4. The cross section of each of the arms Mia, I ob included in these sharply convex surface portions is located approximately at the center of such maximum intensity portion of the magnetic field and effectively cutting across it. By this arrangement, as explained above, the heating is substantially concentrated at the surface portions I87 while the other end of the cross sectional area of each of the arms 50a, iiib extends outside of the maximum intensity portion of the field of its associated coil and into a portion of the field of substantially lesser intensity so that it is heated to a relatively lesser extent.

After the concentrated heating of the surface portions 1%) of the work piece id as described, quenching fluid is supplied to the nozzles 22 from the supply pipe 28 by means of the valve 2i, while these nozzles may be pivotally adjusted to confine the quenching action primarily to the surface portions of the work piece it! on which the heating has been concentrated. By the system described, therefore, the heat treating of a work piece may be substantially concentrated on predetermined sharply convex surface portions while minimizing the heat treatment of other portions of the work piece, thereby minimizing any effect on the structural toughness and elasticity of the work piece as a whole.

In the structure of Figs. 5 and 6, the heating inductor is described as made up of two pairs of inductor coils i5a, I51) and 15c, i512. Electrically the heating inductor #5 should be of such a design although physically it may comprise a group of separate coils or it may comprise a single continuous winding. The latter type of winding is represented in Figs. 7 and 8, which are top plan,

6., and front elevation, views, respectively, of a heating inductor 3B in which one pair of heating coils is electrically provided by the portions 30a, 39b wound and connected to develop magnetic fields in aiding phase and theother pair of coils is electricaliy provided by the portions 380 and 38d similarly wound to provide aiding magnetic fields. The pairs of sections 39a, 3th and 390, Sud, however, are wound and connected to developmagnetic fields opposing each other. relationship has been found most satisfactory in the apparatus of Figs. 5 and 6 for insuring substantially equal heating of the surface portions of. the two arms lEla, 527 of the work piece IB.

While, in the apparatus described, the heating is substantially concentrated at the surface portion iii), there is still very appreciable crowding of the field and consequent concentration of heat at the other sharp edge lily, as shown in Fig. 4. In case it is desired to minimize the heating at this edge, the arrangement of the coils of the heating inductor may be modified. Two such alternative arrangements are illustrated schematically in Figs. 9 and 10. In Fig. 9 the coils 3| and 32 comprising the heating inductor are maintained parallel to each other but are laterally displaced, thereby warping the normal magnetic field to that illustrated. The insertion of the work piece E0 with the cross section of one arm ifib effectively cutting across the maximum in tensity portion of the field, as shown, severely crowds the magnetic field only at the single sharply convex surface portion I of so that the heating is concentrated only at this single surface region. Alternatively, in Fig. 10 the coils 33 and 34 of the heating inductor are arranged at an angle to each other while one arm lilo of the work piece I9 is inserted in the maximum intensity portion of the field between the coils so that only the single sharply convex surface portion if cuts across the field and crowds the field at such point, substantially concentrating the heating effect to the surface portion in this single region. It will be apparent that the heating inductor represented schematically in Figs. 9 and 10 can be embodied in heat treating apparatus of the type illustrated in Figs. 5 and 6.

While there have been described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What I claim as new is:

A high-frequency induction heating apparatus for heating a work piece including two substantially parallel arms, each arm thereof having a sharply convex surface portion, and for concentrating the heating over a predetermined portion of the convex surface of each arm of the work piece comprising, a heating inductor consisting of a continuous winding including two pairs of coaxial coils, the coils of each pair being spaced for the reception of an arm of said Work piece and connected so that their magnetic fields are in aiding phase and the pairs of coils bein closely adjacent and connected so that their fields are in opposing phase, for developing between the coils of each pair a high-frequency magnetic field which, in the absence of a work piece, has a relatively uniform field over its cross-sectional area. and positioning means for locating the work piece with each of its arms extending between the coils of one pair with said predetermined con- This.

, 7 8 vex surface portion thereof effectively cutting Number Name Date across said field. 2,220,002 Rollman et a]. Oct. 29, 1940 HERBERT F. STORM. 2,249,909 Pisarev July 22, 1941 2,254,307 Mott et a1 Sept. 2, 1941 REFERENCES CITED r, 2,290,283 Jones July 21, 1942 The following references are of record in the 2,326,674 101 1943 file of patent: Morey Aug. 31, 2 UNITED STATES PATENTS FOREIGN PATENTS Number Name Date 10 Number Co ntry Date 1,924,296 Stoffel et a1 Aug. 29, 1933 ,3 Great ita n u e 38 1,987,752 Salzman Jan. 15, 1935 2,176,488 Dreyfus Oct, 1'2, 1939 OTHER REFERENCES 2,186,626 Dake Jan. 9, 1940 Machine Design, January 1944, page 115.

2,215,576 Bucknam et a1, Sept. 24, 1940 15 (Copy in Scientific Library.) 

